80W shouldn't trip the house RCD unless the iron is faulty or the plug's wired incorrectly.

It really is worth investing in a variable temperature iron. Much easier to use as you can turn it down for delicate things and up for pot backs etc.

Something like this should be fine..

https://www.jaycar.com.au/60w-esd-sa...e38ff71587f407

Don't be afraid to change the tip type. The bigger tips have more heat capacity and don;t drop the temperature so quickly when doing big items like pot backs.

Keeping the iron clean helps a lot, so always wipe on a damp sponge after use to get the old solder off.

And tinning the surfaces to be joined first helps a lot.